A novel binucleating ligand, N, N'-bis [2-(diphenylphosphino) phenyl] formamidine (Hdpfam) has been prepared and utilized for the synthesis of dinuclear palladium complexes Pd2R2 (μ-X) (μ-dpfam) (R=Ar, Me, X=Cl, Br, I, OH).Hydroxo-bridged complexes Pd2R2 (μ-OH) (μ-dpfam) served as catalyst for the cis-addition of aromatic C-H bonds to alkynes in the presence of catalytic amounts of tri-n-butylborane. In contrast to the Friedel-Crafts type reaction, electron-poor arenes also can be used for the addition reaction. In the reaction of monosubstituted arenes, meta isomers were main products in all cases. The addition of olefinic C-H bonds of indene to alkynes was also achieved by using chloro-bridged complexes Pd2R2 (μ-Cl) (μ-dpfam) and LiAlH (OBut)3 as catalyst. The palladium complexes supported by dpfam catalyzed the cross-addition of triisopropylsilylacetylene to various internal and terminal unactivated alkynes, giving enynes in high yields.
Signal transduction systems for detection of surrounding information are the one of essential functions for life. One of these systems is the sensory system such as vision, olfactory and gustatory. The innate immune system is also fundamental to protect our body, which basically senses microbial components by receptor proteins. In order to elucidate the function of the key molecules in the signal transduction, we have studied it on the view of organic chemistry. Here, the results on the following key compounds will be shown; one is 11-cis-retinal in a light-receptor rhodopsin essential in vision, and the others are bacterial lipopolysaccharide and peptideglycan in the innate immune system.
The development of effective and versatile deuterium labeling methods has been a topic of sustained interest in a variety of fields such as organic, analytical, pharmaceutical, agrochemical, material, and environmental chemistry. Plenty of precedent deuterium labeling methods usually require high temperature and pressure, strong bases or acids, special apparatus, and/or deuterium atmosphere. We developed an effective benzylic site-selective H-D exchange reaction using Pd/C as a catalyst in deuterium oxide under hydrogen atmosphere at room temperature. Application of heat to the Pd/C-H2-D2O system accelerated the H-D exchange and led to the effective deuterium incorporation even on the non-benzylic positions. The use of Pt/C in place of Pd/C made an effective deuteration on the benzene ring possible. In addition, aliphatic compounds were deuterated efficiently by using Rh/C instead of Pd/C. The Pd/C (Pt/C, Rh/C)-H2-D2O system was applicable to the deuteration of bioactive molecules such as amino acids, nucleic acids, pharmaceuticals, and agrochemicals. The features of the present method using Pd/C (Pt/C, Rh/C)-H2-D2O system are reliability, simplicity, and efficiency.
A design of a chiral ligand and the metal-coordinated catalyst is very important for achievement of a high optical purity in a catalytic asymmetric reaction. Recently, we developed the chiral N-P, S-P, and S-S ligands having N, O acetal and S, O acetal structures, such as phosphinooxazolidine (POZ), phosphinooxazinane (POZI), phosphinooxathiane (POT), and sulfideoxathiane (SOT). They afforded products in an excellent enantioselectivities in Pd-catalyzed asymmetric allylic alkylation, amination, and tandem allylation. Furthermore, novel catalytic asymmetric synthesis of ent-CP-99, 994 and ent-L-733, 061 were accomplished by using Pd-catalyzed allylic amination as a key reaction. Cationic Pd-POZ or Pd-POT catalysts demonstrated high levels of catalytic activity in the asymmetric Diels-Alder (DA) reactions of some dienes with oxazolidinone or pyrazolidinone typed dienophiles. Cationic Pd-POZ catalyst showed an excellent catalytic activity in the DA reaction in ionic liquid (IL). The catalyst could be reused eight times without significant decrease of yield and enantioselectivity in the use of IL/CH2Cl2 as a solvent. The review summarizes these our studies.
A single crystal X-ray diffraction method is the most powerful technique for the crystal structure determination of both organic and inorganic compounds. However, a number of organic compounds crystallize in a form of polycrystalline powder rather than a single crystal of suitable size and quality for X-ray crystallographic analysis. Recent remarkable developments of both software and hardware have turned X-ray powder diffraction method into another significant technique for solving crystal structure. In fact, not a few crystal structures solved from the powder diffraction data of organic compounds have been published in scientific papers. At the same time, however, it is also true that crystal structure solution from powder data is still a challenging subject; indeed, the structure solution cannot be executed in such an automatic manner as established in the single crystal method. In this article, we describe the details of the structure solution processes from X-ray powder diffraction data, together with the experimental know-how gained from our experiences.
Organoheteroatom compounds of phosphorous and sulfur are important in relation to the development of biologically active substances and materials. Conventional synthesis in general employed substitution reactions of organohalogen compounds with heteroatom reagents. It was considered that i) the addition reaction to unsaturated compounds; ii) the substitution reaction of C-H bond; iii) single bond metathesis would be more favorable, since the starting materials are readily available, and the reactions are atom-economical. Described here is the use of transition metal catalysis for such syntheses of organosulfur and organophosphorous compounds.
Halichondrin B is a polyether macrolide that exhibits an extraordinary cytotoxicity in vitro and antitumor efficacy in vivo. A structurally simplified macrolactone right half segment of harichondrin B was identified to retain the potent cell growth inhibitory activity of the natural product in vitro. Kishi and coworkers developed a practical, an efficient and scalable synthesis of the right half segment of harichondrin B.